The ability to generate special purpose maps easily by computer from geographic data bases is having a profound effect on cartography. Computer generated maps offer many advantages over using traditional paper maps, such as being able to customize the area, scale, projection, features shown, etc. Users can rid displays of the incidental features (clutter) usually present on printed maps. They have a new found freedom to select the most suitable from a wide variety of projections without being concerned with custom drafting and reproduction costs.
The earliest computer generated maps resembled line drawings, where regions are depicted by their outline. With the use of line maps, however, there is sometimes confusion about which side of a shoreline is land or water, particularly at large scales. A polygon based map provides the option of portraying regions by shading or color. Although more difficult to produce, polygon maps are much easier to interpret, and are generally more pleasing to work with. Another limitation of early soft copy map portrayals was the controlling means lacked a total flexibility for selecting regions of the world, local or global. Most early mapping systems included only a limited number of familiar projections and did not provide correct clipping of features and overlays.
Thus, a continuing need exists in the state of the art for a versatile and reliable apparatus and method to display world maps from digital data, as well as to present user specific overlay data that are totally adaptable with regard to center point and area coverage. The need exists in the state of the art for a versatile and reliable apparatus and method that may be adapted to any one of a large number of map projections and have the capability to display land, water, or other areal features as color filled regions with lakes, rivers, roads, railroads, and other boundaries and to enable a user to pick any point on the currently displayed map and retrieve its geographic location.